In fill level sensors operating according to the FMCW or pulse transit-time method, electromagnetic or acoustic waves are emitted in the direction of a feed material surface. Subsequently the sensor records the echo signals reflected by the feed material and by the container internals and from these derives the respective fill level. Other fill level sensors operate according to the principle of guided microwaves.
A method used according to the current state of the art is essentially based on spurious echo storage that is carried out by a user when the container is empty.
DE 33 37 690 A1, DE 42 34 300 A1, EP 16 281 19 A1, U.S. Pat. No. 7,284,425 B2, WO 2009/003700 A1, EP 21 482 19 A1 describe known methods.
The methods described therein may inadequately fulfil the task of reliably identifying the fill level echo when spurious echoes are present.
The user of a fill-level measuring device cannot always be expected, within the context of commissioning the sensor, to carry out spurious echo storage when the container is empty. In particular in the case of procurement as a replacement part in ongoing operation, it happens time and again that the container to be measured is completely full of material. Nevertheless, a newly installed fill level sensor is to ensure reliable measuring.
The method for identifying the fill level echo based on continuous time shift in successive receiving phases has up to now been reaching its limits in practical applications. The implementation of a robust algorithm to detect time shifts of individual echoes is a requirement for reliable application of the method. Known methods to detect movements by means of tracking to be carried out in advance also do not obviate the need for a robust method. Thus, in the context of a tracking method it can happen time and again that echoes are incorrectly allocated to existing tracks, which will result in incorrect determination of the movement information.